The invention presented here relates to a device on a spacecraft comprising a first craft part, a second craft part detachable from the fist craft part, as well as a clamp, in which there is a prestress that is released on separation, for connecting these said parts.
The use of a so-called clamp comprising shoes and a band to effect a detachable connection between a satellite and a carrier rocket is known. In the assembled state the shoes bear on cylindrical structural parts of the satellite and the carrier rocket""s adaptor at the same time as the band is prestressed around the shoes so that these exert compressive forces on the structural parts. This prestress means that in the band and the adjoining structural parts there is stored strain energy, which is released when the satellite separates from the carrier rocket.
For the separation of the satellite and carrier rocket from each other, the band comprises an opening mechanism, which almost instantaneously opens the band. The opening mechanism normally operates by some pyrotechnic powered separation device. When the stored strain energy is released, it is converted to kinetic energy, mainly in the form of vibrations in the structural parts and translation motions in the end of the hand. The vibrations jeopardize damaging sensitive instrumentation in the satellite, and the band movements may interfere with the satellite. It is obvious that the heavier the satellite, the harder the clamp has to be tightened and the greater the strain energy stored in the band and in adjoining structural parts.
According to an embodiment of the present invention a device on a space craft is provided comprising a first craft part, a second craft part detachable from the first craft part, as well as a clamp, in which there is a prestress that is released on separation, for connecting these said parts, wherein the device comprises at least one energy storing means devised to convert, during separation, at least part of the prestress-stored strain energy to rotational energy.
It is usual for the first craft part to be comprised of a carrier rocket and the second craft part to be comprised of a satellite, but it may as well be so that the first craft part is a satellite and the second craft part is a probe or other examples of combinations of craft parts.
In one embodiment, the energy storing device is realised by two fitting parts, each attached to a respective band end, with a threaded section for engaging with a complementary threaded section present in a connecting device devised to link the ends of the clamp to each other, whereby, during separation, the fitting parts and the connecting device are devised to rotate in relation to one another. On rotation the fitting parts move axially outwards in relation to the connecting device, whereby the stored strain energy in the clamp and the structural parts decreases.
In this embodiment axial loads are kept internally in the connecting device and the fitting parts and do not need to be borne by the bearing between the connecting device and its fastening device. This permits a simple construction for the connecting device, without the need for, for example, axial needle roller bearings, which tend to function unsatisfactorily at high revolutions.
In order to obtain a balanced construction, where little or no axial loads, from the prestress forces in the fitting parts, need to operate on the connecting device, the complementary threaded sections are essentially coaxial in the connecting device.
In a preferred embodiment the fitting, parts and the connecting device are designed in such a way that the process of separation is sufficiently long to allow the occurrence of vibrations in at least part of the craft part to be, at least partly, prevented.
The threaded sections and their complementary equivalents are preferably designed so that a tensile force caused by said stress action, between each fitting part and the connecting device, during separation causes them to rotate in relation to one another.
In this embodiment a retaining mechanism is devised to lock the engagement so as to maintain the prestress, so that actuating the retaining mechanism out of position induces initiation of the separation.
Preferably, the threaded sections of the fitting parts have opposite thread directions and the fitting parts are prevented from rotating. In this embodiment, the retaining mechanism prevents the connecting device from rotating, which means that, during separation, only the connecting device rotates in order to disengage. A suitable connecting device would be a flywheel.
The threaded sections of the fitting parts have male threads while the threaded sections of the connecting device have female threads.
In a simple and practical embodiment, the connecting device and the fitting parts are at least partly contained in a housing, mounted on one of the craft parts, designed to prevent rotation of the fitting parts.